One example of a coding scheme that can be utilized for transferring data is bi-phase modulation. Each bit-window (i.e., period) of a bi-phase modulated signal represents a single logic bit, with each bit-window beginning with a logic state transition. A logic-low is represented by a substantially constant logic state through the bit-window, whereas a logic-high is represented by an additional logic state transition in the approximate center of the bit-window.
When the amplitude of a bi-phase modulated signal is sufficient, any of a variety of different decoding algorithms can be implemented to decode the bi-phase modulated signal. However, as the amplitude of the signal decreases, such as due to filtering and/or transmission medium losses, decoding the bi-phase modulated signal can be difficult based on noise being more likely to appear as valid logic transitions. In addition, in some bi-phase modulated signal transmission implementations, there may be no external clock to align the phase and/or frequency of the bi-phase modulated signal, which can further complicate decoding of the bi-phase modulated signal. Furthermore, when a bi-phase modulated signal is low-pass filtered, such as to remove a carrier frequency, the amplitude of logic-high codes can be attenuated more than logic-low codes that are half the frequency of the logic-high codes.